Experimenting with Geiger-Müller Tube: Half-Life of Protactinium (Pa)

[_Mayday_]

Hey,

On Monday I am doing an experiment to determine the half-life of protactinium (Pa), using a Geiger-Müller tube. The experiment itself is very straight forward and simple, but I have 70 minutes to do it in, which is a lot of time. I was wondering if there was anything else I could do with this apparatus to make the time left over constructive? I have already used to to measure how penetrating certain particles are through different materials.

The 70 minutes does not include time for writing up, so it is a long time, any ideas would be great.

Thanks.

 

[PiratePhysicist]

Well, if it rains around then (don't know what part of the world you're in) you could collect some rain and measure the events per second from the fresh rain water (it was just a good ways up in the sky and exposed to cosmic rays, should have some radioactivity to it). Not difficult or anything, but mildly interesting just to see how radiactive rain water is. Of course I don't know how your teacher/TA/whatever would feel about you bringing water near the Geiger-Muller tube (probably not that expensive but it sucks to have to replace lab equipment).

 

[Loren Booda]

Explore what might create a false positive with your counter.

How about variations in radiation intensity with direction?

Is there any significant (Radon) radiation from concrete vs. other building materials/soil?

 

[_Mayday_]

Explore what might create a false positive with your counter.

How about variations in radiation intensity with direction?

Is there any significant (Radon) radiation from concrete vs. other building materials/soil?

Could you please expand a bit on that. What do you mean by a false positive? Thanks

Well, if it rains around then (don't know what part of the world you're in) you could collect some rain and measure the events per second from the fresh rain water (it was just a good ways up in the sky and exposed to cosmic rays, should have some radioactivity to it). Not difficult or anything, but mildly interesting just to see how radiactive rain water is. Of course I don't know how your teacher/TA/whatever would feel about you bringing water near the Geiger-Muller tube (probably not that expensive but it sucks to have to replace lab equipment).

I might try that if it's rainy tomorrow thank you.

 

[Astronuc]

I think what Loren Booda is suggesting is to do a background count, i.e. with the Pa source away from the detector. Due to low counting rates, a background count would take longer to achieve good statistics.

To measure the half-life (or decay constant) one usually has to do two measurement over some period of time. Then there are the two counting periods and the waiting period in between. Otherwise, one counts for one period, but one must know the mass of isotope present in order to determine the decay constant from the activity.

What is the pedigree of the Pa sample? Does one know the isotopic vector?

See this taken from ( www.nndc.bnl.gov/chart ). Use cursor to find Pa click on chart, then click on 1 under Zoom to see the details.

http://img213.imageshack.us/img213/8680/z91n139zl1ct12r4057sl3.png

 

[Loren Booda]

Thanks, Astronuc, background count.

 

[rgomaa]

Dear Sir,

I need to ask about the Geiger Muller tube that is used for radiation detection in Japan by public. What if the GM exposed to radiation dose (gamma or beta) more than its limit but it wasn't connected to the high voltage which activate it, (Current+ cathode+ anode>> ionization+ cpm). Was this dose accumulated in the GM and as turn it on it will give indication for the high dose or not?

Thank you
BR